(i) Technical Field
The present invention relates to a method for fabricating a semiconductor device.
(ii) Related Art
Nitride semiconductors are used in semiconductor devices such as an FET (Field Effect Transistor). In order to protect a nitride semiconductor layer, an insulating layer that covers the nitride semiconductor layer may be provided. For example, Japanese Patent Application Publication No. 2010-166040 discloses an arrangement in which a protection film made of silicon oxide is provided on a nitride semiconductor layer.
Conventionally, the capacitance of the semiconductor device, which may include the intrinsic capacitance and the parasitic capacitance, may change due to an oxide layer formed on the surface of the nitride semiconductor layer. Variation in the capacitance may drift the gain. Further, electrons are captured in electron traps in the insulating film, so that the current of the semiconductor device may change. Conventionally, it is difficult to suppress both variation in the capacitance and that in the current.